1. Field of the Invention
The present invention relates to a microspeaker and a method of designing the same, and more particularly, to a microspeaker having a high sound pressure level (SPL) and a broad frequency range by using multi-polar permanent magnets which have different magnetization directions and a vibrating diaphragm which has a ferromagnetic material and a multi-layer structure, and a method of designing the microspeaker.
2. Description of the Related Art
Speakers convert electrical signals into voice signals and are applied in various sound devices. In particular, speakers loaded into small-sized sound devices, such as earphones, mobile phones and MP3 players, are called microspeakers.
In order to enhance the performance of a microspeaker, it is required to increase the sound pressure level (SPL) of the microspeaker and broaden the frequency range thereof.
FIG. 1 illustrates a perspective view of and a perspective cross-sectional view of a conventional microspeaker. The microspeaker is formed of a permanent magnet, a yoke, a voice coil, and a vibrating diaphragm.
FIG. 2 is a design model used to analyze the magnetic flux distribution of the microspeaker of FIG. 1 using ANSYS. FIG. 3 illustrates the flow of magnetic flux according to the design model of FIG. 2.
Since the microspeaker is axially symmetrical, the design model illustrated in FIG. 2 is set for half of the region of the microspeaker with respect to a central axis. The yoke collects magnetic flux generated by the permanent magnet and directs the collected magnetic flux toward the voice coil. Referring to FIG. 3, the magnetic flux flows in a direction crossing the voice coil. Powered by current that flows through the voice coil and the magnetic flux that passes through the voice coil, the voice coil moves up and down in a rotational axis direction. In this case, the intensity of a magnetic field, which crosses the voice coil, in a section having a Z value of 5.6 mm through 6.4 mm in FIG. 3 is related to the SPL of the microspeaker. Conventionally, a single permanent magnet (+Mez) in which magnetic flux flows in one direction has been only used.
In addition, it is required to broaden the frequency range of the microspeaker in order to enhance the performance thereof.